Conventionally, a cathode ray tube or a liquid crystal has been used in a display of a computer or the like, and a light emitting diode (LED) or a liquid crystal has been used in a large display on the street, in which a light emitting section is formed in a matrix to constitute each pixel and a displayed image is sequentially changed by turning ON/OFF the pixel.
In the display using the liquid crystal, each pixel is constituted by an indicating section 51 and a thin film MOSFET 52 to be a switching element (control element) as shown in an equivalent circuit diagram of FIG. 12, for example. Gates of the MOSFETs 52 which are arranged in a row direction are connected to a scanning line X and sequentially scanned through scanning lines X1, X2, X3 . . . , and drains of the MOSFETs 52 which are arranged in a column direction are connected to one of data lines Y1, Y2, Y3 . . . . Thus, each pixel is driven by their combination. The reference numeral 53 denotes an auxiliary capacitor for holding a voltage to be applied until the next scan for line-sequential scan.
A liquid crystal layer is a kind of capacitor, and holds the applied voltage to some extent but cannot hold the same voltage until the next scan for the line-sequential scan through discharge thereof. Therefore, the auxiliary capacitor 53 is provided in some cases. Even this auxiliary capacitor can hold a voltage only until the next scan, and should always apply data even if data for ON/OFF are the same. Also in the case in which another light emitting element such as an LED is used, this phenomenon is generated in the same manner. Particularly, it is necessary to rewrite approximately 60 times per second in the case in which a dynamic image is to be displayed.
As described above, in the conventional display device, the data for turning ON/OFF each pixel to display an image should be always applied every constant time even if the ON/OFF of the pixel is not changed. In the case in which a dynamic image is to be displayed, particularly, the data should be updated at a rate of approximately 1/60 sec. Even if the data to be updated are almost the same, all the data should be applied to each pixel at each time. So, great power is consumed for rewriting the data. Although it is necessary to drive by a small battery in a very small portable head mounted display such as a microdisplay or the like, the size of the battery should be increased by the consumption of the great power. Therefore, practical use has become a problem.